1. Field of the Invention
The present invention relates generally to the field of jam-locking nut and bolt assemblies. More specifically, it relates to a jam nut apparatus for fastening to the threaded end of a bolt such as a lawn mower blade mounting bolt to secure the bolt against disengagement. The apparatus includes a tubular end cap and a locking nut.
The tubular end cap has a tubular wall with a threaded inner surface opening at a cap open end for engagingly receiving the threaded end of a bolt and a cap closed end having a cap end wall for abutting the end face of the inserted bolt. The cap also has an external threaded surface about which the locking nut engagingly fastens, and has a reduced diameter locking rim portion extending coaxially from the cap open end, having an inwardly beveled locking rim edge. The locking nut has an inwardly directed, radial locking flange at the nut outer end which fits around and over the cap locking rim portion when the locking nut is fastened onto the cap. The cap also has a hex head extending radially from the cap closed end to permit tightening of the cap with a wrench. The locking nut also has a hexagonal circumferential outer surface for wrench engagement. The internal cap threads are right-handed to receive a conventional bolt end. The external cap threads and locking nut threads are left-handed.
To use the inventive apparatus, the locking nut is fastened around the cap and the cap is fastened onto the bolt threaded end. Then the locking nut is rotated snugly against the member being secured. In this way, friction between the cap, and the locking nut and the member being secured prevent relative movement between the cap and the bolt, and thus hold the bolt assembly together against vibration. The cap is removable from the bolt by first rotatingly backing the locking nut away from the member being secured.
2. Description of the Prior Art
There have long been locking nut assemblies for removably securing bolts and studs. These assemblies have generally either been complicated or expensive, or not designed to secure a bolt of the type often used to mount lawn mower blades.
Fuller, et al., U.S. Pat. No. 5,205,693, issued on Apr. 27, 1993, discloses a quick-release bolt. A lawn mower bolt is provided in the form of an elongate shaft having a circumferential channel recessed around the fastening end. A bolt cap having a tubular side wall slides over the bolt fastening end. Opposing angled slots are provided in the tubular side wall to guide a pin riding laterally in each slot into the cap sufficiently to enter the recessed bolt channel and thus hold the bolt fastening end within the cap. An outer collar member fits around the cap and contains a spring-loaded washer which biases the pins into their slots and thus biases the apparatus to engage the bolt. Sliding the collar against the washer and against spring-loading moves the pins outwardly in their slots and clear of the channel to free the bolt to slide out of the cap when desired. The present invention provides a simpler, more rigid engagement apparatus.
Curran, U.S. Pat. No. 2,696,236, issued on Dec. 7, 1954, reveals a lock nut assembly including a special bolt and threaded outer and inner tube members. The bolt having a main shank is inserted through an opening in sheet stock and the threaded outer tube is screwed over the bolt until snugly seated. The bolt has a reduced diameter shank extending coaxially from its inserted end having other-handed threads relative to the bolt main shank. A locking flange protrudes radially inwardly from the outer tube member adjacent the inserted end of the bolt main shank. The inner tube member, also having other handed threads, is screwed over the reduced diameter shank of the bolt. An outwardly directed radial flange is provided on the inner tube member which rides against the outer tube member inwardly directed locking flange to make tight, high-friction contact. The edges of the inwardly and outwardly directed flanges are cut into V-shaped teeth for tool engagement during fastening and unfastening. A problem with Curran is that it cannot be used with a conventional bolt, and the need to manufacture a special bolt substantially increases its cost. Furthermore the inner tube member is so comparatively small that it might be easily lost.
DeFusco, U.S. Pat. No. 4,043,239, issued on Aug. 23, 1977, discloses a shim nut and screw bolt assembly. A bolt is inserted through a hole in a first sheet member to be secured. A second sheet member to be secured has a flanged opening with internal threads, and an externally threaded sleeve member is screwed into the flanged opening, so that it protrudes a distance out of the second sheet member, opposite the flange. This distance approximates the desired shim distance between the first and second sheet members. The bolt is screwed into the sleeve member, engaging internal sleeve member threads. A nylon button is provided in a cavity recessed into the threaded inner sleeve member surface. The bolt advances against and over the button, meeting friction resistance as it deforms the button. This causes the rotation of the bolt to turn the sleeve member, in turn causing the sleeve member to ride against and abut the first sheet member from one side. At the same time, the head of the bolt rides against and abuts the other side of the first sheet member, causing a locking engagement while maintaining the shim spacing. A problem with DeFusco is that its locking ability depends on the integrity of the nylon button, which could melt or otherwise deteriorate with age and use. Another problem is that the design of DeFusco largely limits its use to its intended shim application between sheet members.
Popp, U.S. Pat. No. 5,152,649, issued Oct. 6, 1992, reveals an expansion sleeve device for setting an anchor in a concrete slab. Popp includes an axially extending expansion sleeve and an axially extending anchor rod. The anchor rod head and much of the anchor rod shank are inserted into a hole in the slab of concrete, the anchor rod head being beveled outwardly toward the end of the hole. The expansion sleeve is fitted snugly around the shank of the anchor rod within the hole adjacent the anchor rod head, and has in inner diameter smaller than the diameter of the anchor rod head. The other end of the anchor rod is threaded and protrudes out of the concrete slab. A tubular liner is screwed over the protruding anchor rod end, and a shaft element extends from the liner coaxially with the rod, and has a hexagonal head. The head is rotated and bears against a collar member surrounding the liner, which in turn bears against the slab surface to draw the beveled head of the rod into the expansion sleeve, spreading the sleeve end and locking the anchor rod into the concrete slab. A problem with Popp is that its use is largely limited to anchor bolts, because it must axially advance the bolt into a locking position.
Orban, et al., U.S. Pat. No. 5,253,967, issued Oct. 19, 1993, teaches an adaptor assembly for tensioning threaded fasteners and a method of tensioning. A bolt to be tensioned is mounted in a structure of which the bolt is to become a part, so that the bolt threaded end protrudes. An internal sleeve having external threads and internal threads screws over the bolt end. An outer sleeve screws onto the external threads of the internal sleeve to rotate to abut and transfer bolt loading to the structure. A remote edge of the outer sleeve includes teeth which are engaged by a beveled gear mounted in a housing. A bolt tensioning element screws into the internal sleeve opposite and coaxially with the bolt end and stretches the bolt, moving the internal and outer sleeves away from the structure. As the bolt is stretched, the beveled gear is rotated to reposition the outer sleeve against the structure to transfer the tensile loading of the stretched bolt to the structure so that the tensioning element can be removed. A problem with Orban et al., is that the bolt must be stretched to cause the adapter assembly to lock. Orban et al. is also relatively complex and expensive to manufacture.
Bittern, U.S. Pat. No. 3,784,316, issued Jan. 8, 1974, teaches a hole saw reversible, quick-disconnect drive apparatus. The Bittern drive apparatus has a stud portion threaded in one direction at a first segment to cause engagement of a spring clutch assembly to rotate a hole saw blade. The stud portion is also threaded in the other direction at a second segment to cause disconnection of the apparatus from the hole saw blade. A problem with Bittern is that it locks only as long as torque is applied in one direction, but does not provide a reliable lock absent applied torque.
It is thus an object of the present invention to provide a bolt locking jam nut apparatus which can engage a conventional bolt.
It is another object of the present invention to provide such an apparatus which is inexpensive to manufacture.
It is still another object of the present invention to provide such an apparatus which is sturdy and reliable.
It is finally an object of the present invention to provide a method of using the apparatus which is simple to understand, easy and requires only ordinary tools.